Xtian Bible "Prophecy" Demolished

[Minimalist]

A very good question and one for which there is no easy answer. There are numerous problems with the traditional dating, not the least of which is that we have no evidence of this kind of literature in even the relatively advanced northern kingdom in the 8th century BC although we do have indications that they had at least become literate enough to keep records and inventories. But monumental architecture and inscriptions are scarce and while there are Moabite and Aramaic inscriptions the Israelites don't seem to have done much writing. The possibility exists that these were oral tales later embellished or re-written to suit the needs of other powers/authorities. As noted in the OP scholars already think that this tale was a composite writing anyway.
Generally, as we have no evidence of Hebrew texts prior to the Dead Sea Scrolls in the 2d century BC it seems likely that this stuff was written later rather than earlier.

Also the references to Assyria in that "prophecy" could be referring not the Assyrians such as such, rather an enemy that could be compared to the Assyrians.

Babylon took out the Assyrians. Why not call them Babylonians? After all Judah was done in by Babylon not Assyria. It's a good point but I think I'll leave rampant speculation to the fundies if they ever grow a set and try to defend their fairy tales.